Air pump



FIG. 1 is a perspective view of an air pump showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines shown on the drawings depict portions of the air pump that form no part of the claimed design. 

CLAIM The ornamental design for an air pump, as shown and described. 